The present invention relates to a convex lens assembly designed for use in a supermarket, shop, etc., for monitoring a particular area, and more particularly to such a convex lens which is easy to install and inexpensive to manufacture, and can be conveniently adjusted to the desired angle.
FIGS. 1 and 2 show a convex lens assembly according to the prior art. This structure of convex lens assembly comprises a back board holding an acrylic convex lens, and a mounting frame adapted for securing the back board to support means of a building. This structure of convex lens assembly is somewhat functional, however it has numerous drawbacks as outline hereinafter.
1. The assembly process of the back board and the acrylic convex lens is complicated because it is done by: marking four equiangularly spaced through holes at the back board around its border, then mounting a packing rubber around the border of the convex lens and the back board, then attaching four clamping plates to the convex lens and the back board to hold down the packing rubber, and then fastening screws to a respective through hole of the clamping plates and the through holes of the back board to secure the clamping plates in place.
2. The back board must be made with four equiangularly spaced through holes at the center so that four screws which are mounted with a respective washer can be inserted through the through holes from the inner side of the back board to its outer side and then through four locating holes in corners of a ball socket and then fastened up with a respective nut to fix the ball socket in place. When the ball socket is installed, three screws are respectively fastened to three screw holes of the ball socket to fix a socket cover to the ball socket, permitting a ball head connecting rod to be retained to the ball socket. However, when fastening the socket cover to the ball socket, the direction of the radial opening of the socket cover must be accurately confirmed so that the ball head connecting rod can be turned to the desired angle. If the radial opening of the socket cover is not set in the correct direction, the socket cover must be disconnected from the ball socket and installed in the correct position again.
3. When the mounting base and supporting bar of the mounting frame are fixedly connected together, an extension bar may be used and connected between the ball head connecting rod and the supporting bar to extend the space between the back board and the support means of the building. However, because the mounting holes of the supporting bar and the mounting holes of the extension bar and round holes, two hand tools must be used to hold a screw and a nut respectively so that the screw and the nut can be fastened up to fix the supporting bar and the extension bar together.
4. The whole assembly of the convex lens assembly is complicated because it is comprised of a big number of parts including the back board, the convex lens, the ball socket, the ball head connecting rod, screws, the socket cover, the rubber packing strip, the clamping plates, screws, washers, screws, nuts, mounting base, supporting bar, extension bar, screw, and nut. Processing the back board with holes is also a complicated job.
5. When a screw drops to the inside the ball socket must be disconnected from the ball socket cover so that the fallen screw can be taken out.
The present invention has been accomplished to provide a convex lens assembly which eliminates the aforesaid drawbacks.
According to one aspect of the present invention, the convex lens assembly comprises a back board holding a convex lens, a mounting frame fastened to a support of a building, the mounting frame comprised of a mounting base, an extension bar, and a supporting bar connected between the mounting base and the extension bar, a ball socket fastened to the back board, a socket cover fastened to the back board to hold down the ball socket, and a ball head connecting rod having a ball head at one end coupled to the ball socket and threaded rod at an opposite end fixedly connected to the mounting frame, wherein the back board is integrally molded from impart resisting plastic, comprising an annular groove at its front side near the border which receives a flanges border area of the convex lens, a plurality of locating rods equiangularly spaced along therannular groove and pressed at the flanges border area of the convex lens to hold down said convex lens, a circular mounting hole at the center of its back side which receives the ball socket, and a plurality of locating notches equiangularly spaced around the circular mounting hole of the back board; the socket cover comprises a plurality of threaded locating strips perpendicularly raised from the border of its circular base and respectively inserted through the locating notches of the back cover within the circular mounting hole of the back board and then fixed in place by a lock nut. According to another asepct of the present invention, the mounting holes of the supporting bar of the mounting frame and the mounting holes of the extension bar are square holes; the screws which are used to fix the supporting bar to the mounting base and the extension bar have a square shoulder fitting the respective mounting holes of the supporting bar and the extension bar. By means of this arrangement, the nuts can be conveniently threaded onto the screws to fix the extension bar and the supporting bar together without using a hand tool to hold the screws. According to still another aspect of the present invention, one locating notch of the back board has a relatively greater size than the other locating notches of the back board; one locating strip of the socket cover has a greater size than the other locating strips of the socket cover, the bigger locating strip of the socket cover being aimed at the notch of the socket cover and fitting the bigger locating notch of the back board. Therefore, the socket cover can be quickly installed in the correct direction.